---
title: "Properties of hardened concrete"
subject: "Concrete Technology and Masonry Structure"
chapter: 4
key: "semester_5/concrete_technology_and_masonry_structure:hardened-concrete-properties"
source: https://www.bctengineer.com/q/semester_5/concrete_technology_and_masonry_structure/hardened-concrete-properties
site: BCT Engineering
---

# Properties of hardened concrete

Concrete Technology and Masonry Structure · Chapter 4: Properties of hardened concrete

- Asked in: 2079 Baisakh, 8 marks; 2076 Chaitra, 4 marks; 2074 Chaitra, 6 marks (asked 3 times)
- Video: [Concrete Technology - Part 15 - Hardened Concrete](https://www.youtube.com/watch?v=daSUi4RUZe4) — Civil Basic Course
- Answer checked by Claude Sonnet 5.5 on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_5/concrete_technology_and_masonry_structure/hardened-concrete-properties
- Whole chapter: https://www.bctengineer.com/md/semester_5/concrete_technology_and_masonry_structure/chapter-4

## Question

Explain the properties of hardened concrete.

## Short answer

Hardened concrete properties include compressive and tensile strength, modulus of elasticity (Ec=5000√fck), shrinkage strain of ~0.0003, creep coefficient1.1–2.2, durability, permeability, and density (2400 kg/m³ plain,2500 reinforced). Strength increases with lower w/c, good compaction, and curing.

## Answer

Hardened concrete properties decide the performance of a structure in service. The main ones:

#### 1. Strength
- **Compressive strength:** the basic property, tested on 150 mm cubes at 28 days (IS 516); characteristic strength $f_{ck}$ is the value below which not more than 5% of results fall (IS 456, Cl. 2.2). Grades M20 to M40 are common.
- **Tensile strength:** direct tension is difficult to test, so the splitting test or the flexure test is used. Split tensile strength is about $0.5\sqrt{f_{ck}}$ to $0.6\sqrt{f_{ck}}$, and IS 456 (Cl. 6.2.2) gives the flexural strength as $f_{cr} = 0.7\sqrt{f_{ck}}$.
- **Shear and bond strength** (design shear stress $\tau_c$ from IS 456 Table 19; bond stress $\tau_{bd}$ from Cl. 26.2.1.1).

#### 2. Elasticity
The stress-strain curve is non-linear. The short-term modulus is $E_c = 5000\sqrt{f_{ck}}$ N/mm$^2$ (IS 456, Cl. 6.2.3.1). Poisson's ratio is 0.15 to 0.20.

#### 3. Volume change and time-dependent behaviour
- **Shrinkage:** strain about 0.0003 (Cl. 6.2.4).
- **Creep:** creep coefficient 1.1 to 2.2 (Cl. 6.2.5.1).
- **Thermal:** coefficient of expansion about $10\times10^{-6}$ per °C.

#### 4. Durability and permeability
Resistance to water penetration, chemicals, freeze-thaw, abrasion and carbonation; it depends on W/C, cement content and compaction (IS 456 Tables 4 and 5).

#### 5. Other properties
- Density (unit weight): 2400 kg/m$^3$ for plain concrete and 2500 kg/m$^3$ for reinforced concrete (IS 456, Cl. 19.2.1).
- Fatigue resistance, impact resistance and fire resistance.

Strength increases with age, lower W/C, good compaction and good curing.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. Characteristic strength f_ck is the value below which:
   A. 50% of results fall
   B. not more than 5% of test results fall
   C. no result falls
   D. 10% of results fall
   Answer: B. IS 456 defines f_ck with a 5% defective fraction. (Key point: Characteristic strength)

2. Flexural strength of concrete per IS 456 is about:
   A. 0.7 sqrt(f_ck)
   B. 5000 sqrt(f_ck)
   C. 0.7 f_ck
   D. f_ck/10 only
   Answer: A. f_cr = 0.7 sqrt(f_ck) N/mm^2; E_c = 5000 sqrt(f_ck). (Key point: Tensile strength)

3. IS 456 creep coefficient for concrete ranges from:
   A. 0.1 to 0.5
   B. 3 to 5
   C. 1.1 to 2.2
   D. 0.0003 to 0.0008
   Answer: C. Theta is 2.2, 1.6 and 1.1 for loading at 7 days, 28 days and 1 year. (Key point: Creep coefficient range)

4. Permeability and durability of hardened concrete depend mainly on:
   A. colour of cement
   B. size of formwork
   C. time of casting only
   D. W/C ratio, cement content and compaction
   Answer: D. Low W/C, adequate cement and full compaction give dense, durable concrete. (Key point: Durability dependence)

## Related in Concrete Technology and Masonry Structure

- [Hardened concrete properties; elastic behaviour](https://www.bctengineer.com/question.md?key=semester_5%2Fconcrete_technology_and_masonry_structure%3Ahardened-properties-elastic-behaviour) — Concrete Technology and Masonry Structure, chapter 4
- [Physical properties of OPC and concrete behaviour](https://www.bctengineer.com/question.md?key=semester_5%2Fconcrete_technology_and_masonry_structure%3Acement-physical-properties) — Concrete Technology and Masonry Structure, chapter 1
- [Aggregate properties and their influence on concrete](https://www.bctengineer.com/question.md?key=semester_5%2Fconcrete_technology_and_masonry_structure%3Aaggregate-properties-influence) — Concrete Technology and Masonry Structure, chapter 1